The 114th Congress began meeting for the first time on Monday as President Barack Obama returned from his vacation in Hawaii.

The Republican Party now controls the United States Congress. Voters elected enough Republican candidates to give that party majorities in the House and Senate in elections last November. Political observers say the next two years will be difficult for both President Obama, a Democrat, and his political opponents.

Mr. Obama will have to defend his current policies from change. Republicans must show that they can work with the president on issues that are important to all Americans and to Republican voters.

Senate Majority Leader Mitch McConnell told CNN Sunday that a government divided between a Republican Congress and a Democratic president can still work. He said voters want the government to make progress on important issues.

Republicans oppose the president on health care, immigration and Cuba

However, many Republican lawmakers want to weaken some of the programs approved earlier in Mr. Obama's presidency. They include the Affordable Care Act, which many call Obamacare. It requires most Americans to buy health insurance.

Many legislators also want to end the president's new immigration policy. The policy lets many people who entered the country illegally stay and possibly seek U.S. citizenship. Republicans are also critical of the president's recent decision to open diplomatic relations with Cuba. For more than 50 years, the United States had sought to isolate the communist nation. Many Republicans do not believe that policy should have changed.

Policy towards Ukraine, Islamic State and Iran also in dispute

Republican lawmakers are often quick to criticize Mr. Obama on his foreign policy. Senator Bob Corker will become the new chairman of the Senate Foreign Relations Committee. He had this to say:

"I have no earthly idea how the administration plans to go about degrading and destroying ISIS in Syria."

Senator John McCain has also been critical of how Obama has dealt with the conflict in Ukraine. He said:

"This president (Obama) does not understand Vladimir Putin. He does not understand his ambitions, he does not understand that Vladimir Putin is an old KGB colonel bent on restoration of the Russian Empire."

International negotiations on Iran's nuclear program are to restart in a week. Senator Corker and other Republicans have said lawmakers may support stronger restrictions on Iran if the negotiations fail.

President Obama threatens vetoes

To his critics, President Obama has said he will use his veto power if Congress tries to change his policies.

Other members of Congress have already looked ahead to the next election. Chuck Schumer is a Democratic Senator from New York. He had this to say on CNN's State of the Union program:

"If we put together a strong economic message aimed at the middle class, not only will it unify our party, but we can actually do really well in 2016."